Electric windshield wiper control



p 1, 1953 R. c. BOHL ELECTRIC WINDSHIELD WIPER CONTROL 4 Sheets-Sheet 1 Filed Nov. 3 1950 JNVENTOR ROBERT 0.30m.-

BY M Sept. 1, 1953 R. c. BOHL.

ELECTRIC WINDSHIELD WIPER CONTROL 4 Sheets-Sheet 2 Filed Nov. 3 l 5O INVENTOR ROBERT c. 5011!.

BY M

Sept. 1, 1953 R. c. BOHL ELECTRIC WINDSHIELD WIPER CONTROL 4 Sheets-Sheet 3 Filed NOV. 3 1950 .lh llm INVENTOR ROBERT c. BOHL. v I BY, L z

Sept. 1, 1953 R. c. BOHL ELECTRIC WINDSHIELD WIPER CONTROL 4 Sheets-Sheet 4 Filed NOV. 5 1950 INVENTOR ROBERT BOHL Patented Sept. 1, 1953 ELECTRIC wrNDsnELn WIPER ooN'rRo R bert G- Boh Stiu'te nt, Wis" assl nor to Be m C ny, nc, o osso, Mich, a come:

when of Mic gan Application November 3, 1950, Serial No. 193,977

( ale-1.2.75)

This invention relates to windshield Wipers, and particularly to the electrically driven types of wiper drives.

In electrical systems for driving Windshield wiper operating linkages, it is desirable 1. .0 elude the motor-ener izing circuit some are vision for insuring the stopping of the motor at a predetermined point in its rotary path, corresponding to the point in which the wiper blades will be at the lower limit of their oscillatoxy path. To achieve such a result certain prior art systems have incorporated mechanical braking arran eme ts. and others have employed dynamic braking means in various forms. The present invention utilizes a novel application of the dynamic braking principle, characterized in that, substantially, imultaneously with production of a reverse magnetic efiect across the motor armature, ,to bring it to a stop,

. there is an energization of a thermal unit operating as a circuit breaker. The contact or bridging element of this thermal unit is in the main circuit leading to the motor, and the manner in which this thermal unit cooperates with related parts when the wiper blade has reached the parked position following manual initiation of the stopping (parking) cycle assures mediate armature deceleration to a full stop.

It is accordingly an object of the invention to provide a novel method and means of controlling th point of stopp ng of a wind ield ip by the operation of aut mat c mechanism whose unct oning s und r the control of a s n e man ally operable elemen cr ing as a combined electrical and mech n cal llstrum ntality f r nne c tins the automatic cle ments of the system from operating in any sequence other than the predetermined sequence by which accurate stopping of the mechanism is assured.

Other objects and advantages pertaining to certain features of the disclosed mechanism will be indicated in the following description.

In the drawings Fig. 1 is a View partly schematic and partly mechanical showing the elements entering into the invention as applied to a windshield wiper motor; the relative positioning of the manually operable parts being indicated in the relationships which they occupy while the mechanism is in motion; Fig. 2 is a similar view partly schematic and partly mechanical but with the manually operable elements shown in the relative positions occupied when the mechanism has been, or is about to be brought to a stop, with the wiper blades in parked position; and Figs. and 4 are views correspondin to Fi s. 1 and 2 respec ely, but with modified electrical connections particularly suitable where the. motor to be controlled i of he shunt field type.

n both i ws the windshi ld pe o at n motor is shown schematically s in lud n armature 5 and series field windin s 6 and 1, there being also an indication of an automatic sw tch el ment 8 adapt d o be clos d for an inst n of tim during ach e o uti n of a cambea in switch operatin e ement mounted in the u ual manner the ear tra n (not shown) constitutin par o the opera ing connections be t een sh ft of arm tu e .5 and the wi er blades Such a a -operated switch constitutes a Pa t of sub anti ly al commonl use win shield wi e cont ol ircu ts a d ma be con s d cd cor espond n in g ner lrinc ples to the c m o cr ted witch o he Cores t al.- Pat n no. 2, 64, 03 r the Whit e Pa ent No: 2,870,101, there being no claim ma e he ein to such a oam opc a cd switc per s bu on o the no el intc-, cla iou ps sh wn herein exis ing betw en sa d am o e a d s itch '3 on th one han and the manually c nt olled switc el me ts at H, 4.2, J4, l5, 6 and 1.1 in bot Figures .1 nd 2 and new to be ide scribede sw tch M and 42 one sh wn as rounded projection inte ral w th a s ide-bio push-pull rod 2. hav ng a cur e conduct ng portion .2 Joining th two p o ections ll and 12. Whe rod s n th position ndicated l th said e ements ll, 2 and 2 a e no in bridging re at o ship o h tatio a y mu tacts M and 1- the armature c ont zus'oi ouit t e e ore is nope at due o th nco plete path e en though cam swi ch 8 closes at one a e o each re o u-tion of motor-driven sca carry n the operat n However, upon in o horod 3. to th meme-stoppin p sh 2.9 were is m'ovided a condition of bridging as between the stationary contacts l4 and 15. In addition to the contact bridging function of the element 22 the said element has an appendage 22a whose function is to cooperate mechanically with the adjacent actuating element 26 of a snap-action thermostatic switch 21 of any well known type of manufacture, which switch 21 is shown as having the terminals l6 and I! heretofore referred to. When the elements 22 and 26 are in the abutting relationship indicated in Fig. 1 the said actuating element 26 is shifted to its extreme leftward position and 3; is held in such position by the pressure of the projecting portion 22a of the said element 22. In this leftward position the striker element 26 of the thermostatic switch assembly is in position to operate as an automatic re-setting agency with respect to the thermostatic switch, to permit the latter to return to closed-circuit position when s'ufliciently cooled. On the other hand, when the push rod 2! is moved inwardly to the Fig. 2 position--a manual operating knob l9 being attached thereto as indicated-the ac-' tuating element 26 is no longer restrained by the element 22a. and is accordingly free to snap to' erated cam switch 8 will set up a short circuiting the right just as soon as excessivev electrical current conditions initiate such a CiIClllt-bl'8&king impulse.

The cooperating elements havin n been f,

ing action sufiicient to stall the wiper linkage in scribed, the operation of the system will bereadily apparent. With the parts in Fig. 2 position the circuit to the motor 5 is opened at the switch 21 and the parts are at rest; but as soon as the manually operable rod 2| is shifted to the Fig. 1 position the switch 21 is automatically re-set in the closed position andthe-motor is immediately energized by reason of the current flowing theretoby way of the said thermostatic switch 2! which has now been reset to the circuit closed position by reason of the pressure of the element 22a against the striker-element 26. It will be observed that this motor-energizing circuit is independent of the cam-operated switch 8 and therefore the motor will continue to run and operate the wiper blades notwithstanding the fact that the switch 8 is alternately closed and opened on each revolution of the motor-operated cam element associated therewith.

Now when it is desired to bring the motor and the wiper blades to a stop the rod 2! is manually returned to the Fig. 2 position whereupon the cam rotated by the motor will become elTective, immediately upon the next ensuing closure of the switch 8, to establish a short circuit condition in the-armature windings, the said short circuit being by way of the now bridged contact elements l4 and I5. This short circuited condition will produce such aninstantaneous dynamic braking action as to bring the motor and hence the wiper blades to practically an immediate stop, the blades being thus stopped promptly and positively in the exact predetermined parking position At the same instant the thermostatic switch 21 will be subjected to excessive current flow by reason of the stalled condition of the armature, and this excessive current flow will immediately snap said switch 21 to the open position-the striker element 26 being free to move to the right under this snapping impulse, since the restraining element 22a is now out of its path. Accordingly all current flow now ceases and no further operation of the wiper mechanism will occur until the rod 2| is again shifted to the Fig. 1 setting, to repeat the cycle of events heretofore traced.

Figs. 3 and .4 show one manner in which the electrical connections of Figs. 1 and 2 may be modified for application to a motor with its field winding 6 in shunt with the armature windings 5, rather than in series, as in Figs. 1 and 2. These modifications comprise the addition of a resistor R of relatively low ohmic value, and the addition of a wire 3| connecting contact II with the main conductor 32, as shown at 30, and a wire 33 connecting contact 14 with the armature circuit at 34, to shunt out the resistor R. during normal operation of the motor (Fig. 3 position). Upon shifting rod 2! to the motor-stopping position (Fig. 4) the next ensuing closure of motor-0pcondition' in the armature, by way of contacts [4 and I5, exactly as in the Fig. 2 circuit. This condition immediately establishes a dynamic brakthe parked position of the blades, assuming that the cam switch 8 has been correctly located in relation thereto. At the same time the two parallel circuit branches containing the resistor R and the shunt field winding 6 become effective to draw additional current from the source 10, and this additional current causes the thermostat switch 21 to snap open, as in the Fig. 2 arrangement.

What I claim is:

1. In a windshield wiper control circuit, a source of current, a wiper linkage drive includ ing a motor having armature and field windings, a first circuit including a thermostatic switch connecting said armature and field windings with said source, a periodically closing motor-operated switch, a second circuit including said armature winding and said periodically closing switch, normally separated switchelements in said second circuit, and manually operable motor-starting and stopping means for bridging said normally separated switch elements to create a short-circuiting condition in said'armature winding by way of said second circuit on the next ensuing closure of said periodically closing switch, to exert a dynamic braking efiect on the motor prior to interruption of said first circuit and thereby stall the wiper linkage, said means further operating to cause the opening of said thermostatic switch by reason of the increased current flow in said first circuit as a result of said dynamic braking effect.

2. Wiper control mechanism as defined in claim 1, wherein said manually operable means includes a part engageable with said thermostatic switch to re-set said switch to the closed position only when said manually operable means is shifted to the motor-starting position.

ROBERT C. BOHL.

Name Date Coxon et a1. Dec. 12, 1944 Number 

